Electromagnetic device



July 1, 1930.

c; HALL BLECTROIAGNBTIC DEVICE Filed Aug; 17. 1925 Inventor: ChestePLHaH. by /2 J M".

Hts Attorney.

Patented July 1, 1930 UNITED STATES'OPATENT OFFICE CHESTER I. HALL,

OF FORT WAYNE, INDIANA, ASSIGNOR T GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK memomaens'rro DEVICE Application meaau m 17, 1925. Serial No. 50,545.

My invention relates to, improvements in electromagnetic motion reproducing devices of the ratchet type and in particular to an improved electromagnetic ratcheting relay for demand meters and other electromagnetic counting devices.

A wellknown type of demand meter consists of a friction pointer, a cooperating scale, a dog or pusher arranged to advance the pointer in accordance with the maximum demand of the metered uantity as determined from a plurality of definite time intervals, means for returning the dog to a zero position at theend of each time interval, a pawland ratchet device for advancing the dog and an electromagnet for operating the pawl. In the well known arrangement, the electromagnet is energized intermittently by a contact device driven by a meter. When the electromagnet is energized, the pawl is advanced thereb and when the electromagnet is deenergize a spring returns the pawl to its retracted position.

The source of supply for the electromagnet is generally taken from the most convenient supply system available, either alternating current or direct current, and if this supply system is subject to momentary failure or partial failures in voltage, there exists a source of error for the demand meter which, strange as it may seem, is more liable to produce an overregistration of the demand meter than an underregistration. This source of error may be visualized by assuming that if, when the meter operatedcontact is closed and the ratcheting pawl is in its advanced position, there occurs a momentary failure in the voltage of the source supplying the ratcheting solenoid, such failure w1ll deenergize the solenoid and the spring will return the pawl to a retracted position. If, when the voltage returns, the motor operated contact is still closed, the pawl will again be advanced producing an erroneous corresponding advance of the dog and possibly of the demand pointer.

In my copending application Serial No. 677,557 filed November 28, 1923, assigned to the same assignee as the present invention, I have described a demand meter arrangement for overcoming the disadvantageabove mentioned. In said application the spring which was theretofore used to retract the ratcheting pawl is replaced by an electromagnet. This electromagnet is permanently connected across thesource which supplied the advancing electromagnet. When the advancing electromagnet is energized it overcomes the force of the retracting electromagnet and causes the advance of the ratcheting pawl. When the advancing-electromagnet is deenergized the retracting electromagnet returns the pawl to the retracted position. If the source of supply should fail when the circuit of the advancing electromagnet is closed, both'electromagnets will be deenergized and consequently the pawl will remain in the advanced position until the voltage again comes on and the circuit of the advancing electromagnet is opened. Thus the erroneous operation above explained is avoided. The

resent invention relates to an improvement in this electromagnet return relay mechamsm.

In the arrangement of my copending application above referred to a very strong advancing electromagnet was necessary in order to overcome the holding force due to the magnetic seal between the relay armature and retracting electromagnet so as to start the armature towards the advancing position. I have discovered that this difliculty may be overcome by providing a neutralizing coil on the retractlng electromagnet, which coil is connected in series with the coil of the advancing electromagnet so that when the latter is energized the holding force of the retracting electromagnet is largely destroyed. The features of my invention which are believed to be novel and patentable will be pointed out in the claims appended hereto. For a better understanding of my invention reference is made in the following description to the accompanying drawing in which Fig. 1 represents my invention as ap plied to an ordinary demand meter installation and Fig. 2 shows the invention applied to a duplex demand meter installation.

Referring first to Fig. 1, 10 represents a scale of the demand meter, 11 a friction ointer cooperating with thescale 10, 12 a og'or ll ll of the time interval.

pusher for the friction pointer 11, and 13, a zero stop for the dog 12. The dog is arranged to be advanced through a shaft 1 1 and a train of gears by means of a ratchet wheel 16, pawl 17 and the electromagnetic device shown at 18. The dog is arranged to be returned to the zero position against-stop 13 by means of a spring 19 which is wound up as the dog is advanced and which is released by a timing device at predetermined intervals. A timing device represented'at 2O drives-a cam 21 through a gear train 22. This cam rocks a lever 23 and the lever is arranged when so rocked to slide gear 24, which is spleened on its shaft, out of mesh with the remainder of gear train 15, thereby allowing spring 19 to return the dog 12 to a zero position at the end Aside from the construction and operation of the electromagnetic device 18, the apparatus and the operation thereof is similar to previous instruments of its class.

v The electromagnet device 18 comprises in this instance, two stationary core sections 25 and 26, both arranged to act upon the common armature 29 which moves the pawl 17 through the pivoted lever 30. The part 25 is the advancing section of the device and is provided with the energizing coil 27. The pa rt 26 is the retracting section of the device and is provided with two oppositely wound coils 27 and 28. Coil 27 is connected in series relation with coil 27 and with contacts 32 to a source of supply 31. Coil 28 is permanently connected to the source 31. The contacts 32 are arranged to be opened and closed at arate determined by the rate of operation of a meter represented at 33. Coils 27 and 28 are of equal -or of substantially equal strength so that when both are energized the resultant flux in section 26 of the core is negligible,

The operation under normal conditions is as follows; hen contacts 32 are open the armature 29 is drawn to the right due to the flux produced by the constantly energized coil 28. lVhen contacts 32 are closed the flux produced by coil 27 in core 26 opposes the flux produced by coil 28 in this core so that the resultant flux tending to maintain armature 29 in the retracted position is negligible or substantially zero. The flux-produced by coil 27 in core 25 readily pulls the armature to the advanced position. lVhen the contacts at 32 are opened the flux of coil 28 is again effective to retract the armature.

Now let it be assumed that when contacts 32 are closed the voltage fails. The armature 29 remains in the advancedposition because coil 28 has lost its current with coils 27 and 27 and there is no rorce tending to move the armature. When the voltage again comes on nothing happens until the contacts 32 are opened andthe armature 29is retracted in the usual way. ikewise when the contacts at 32 are open and the voltage failsarmature 29 be made with few ampere turns, resulting in a comparatively small, eflicient, positively operating device.

In Fig. 2 I have represented my invention applied to a demand meter relay as arranged to register the demand of two meters 33 and 34. The demand meter will be similar to that shown in Fig. 1 except for the electroniagnet ratcheting relay represented at 18'.

This relay is provided with the electromagnetic return comprising permanently connected coil 28 and core 26 as in Fig. 1 but has two advancing coils 27 and 37 and two compensating coils 27 and 37. Coils 27 and 27 are connected in series through the meter operated contact 32 and coils 37 and 37 are connected in series through meter operated contact 35. All coils are energized from the common supply source-31. Coils 27 and 37 are wound to oppose the flux of coil 28 and each of these three coils is designed to have the same number of ampere turns. Coils 27 and 37 are wound to oppose each other and are of the same number of ampere turns. The operation of this arrangement is the same as in Fig, 1 for each individual part of the device. Thus when contacts 35 remain open and contacts 32 close and open, the coils 27, 27 and 28 perform the same functions that they performed in the device of Fig. 1. \Vhen contacts 32 remain open and contacts 35 close and open, coi-ls 37, 37 and 28 perform similar functions.

Let us assume that, while contacts 32 are closed and the armature 29 is in the advanced position, contacts 35 close and open. Since coils 37 and 27 are wound in opposition the magnetismof core 25 will be destroyed and since coils 27 and 37 are wound to oppose coil 28 and are both equal in strength to coil 28, core 26 will now have a resultant flux equal to that produced by coil 37 and the armature 29 will be retracted until contacts 35 open and then it will be advanced again. The same result would be produced it contacts 32 opened instead of contacts 35. Consequently the correct number of advances of the ratcheting device will occur under such conditions. There is one possible source of error, and that is when contacts 32 and 35 close simultaneously and then open simultaneously. This possibility is so remote that it may be disregarded. If at any time the voltage should 'fail, all energized coils are deenergized simultaneously and no movement of the armature 'will take place.

Since the device never is called upon to overcome the pull of a spring or of a magnetic seal the coils may be designated with few ampere turns resulting in an eflicient, positively operating device.

I have represented and described certain modifications of my invention as applied to a demand meter of a particular type, but it will be evident to those skilled in the art that various changes, both in the design of the actuating mechanism and the purpose for which it is used, may be made without departing from my invention and I intend to cover in the appended claims all modifications and uses falling fairly within the true spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electromagnetic device comprising an armature, an intermittently energized electromagnet for moving said armature in one direction, a normally constantl energized electromagnet for moving sai armature in the reverse direction, and a coil on said normally constantly energized electromagnet for causing the latter to be ineffective when said first mentioned electromagnet is energized.

2. An electromagnetic device comprising an armature, an intermittently energized electromagnet for moving said armature in one direction, a normally constantl energized electromagnet for moving sai armature in the reverse direction, and a coil on said last mentioned electromagnet connected in series with the energizing circuit of said first mentioned electromagnet for substantially neutralizing the effect of said normally constantly energized electromagnet when said coil is energized.

3. An electromagnetic device comprising an armature, an electromagnet having two substantially equal coils wound in opposltion, the circuits of which are adapted to be independently and intermittently energized for moving said armature in one direction, an electromagnet for moving said armature in the reverse direction having a normally con- 'stantly energized coil and two coils of substantially equal strength to said normally constantly energized coil and wound in opposition thereto and respectively connected in series with the coils on the first mentioned electromagnet, and a common source of supply for all of said coils.

In witness whereof, I have hereunto set my hand this 10 da of Aug, 1925.

(l HESTER I. HALL. 

